I guess the client side is missing the state to render the app correctly. You need to pass down the app state to the client. This is also called rehydration.

You can do this by serializing your state on the server and sending it down as a JSON string with the rendered html. On the client side you can parse the serialized state and use it as an initial state when creating the store. This will result in both renders, the server and the first client side one, to produce the same markup --> the checksum equals.